I'm affraid You're out of luck fighting a beaver in a water war. I trapped beavers many years and you can't stop them You can only try and contain them. What's wrong with just letting the water go over the top of the beaver dam?
Beavers sense running water. They find it, and they stop it.
Having said that, here's what I would do. Put your intake as far upstream of the dam as possible. Use the intake screen that is used for a siphon drain (big surface area) and put it near the bottom of the pond. (it will stay clean) Run your drain pipe upwards out through the dam with the discharge at your desired water level. Water pressure will push the water out the end of the pipe and the beavers won't be able to get to it.
Hopefully, they won't sense the low flow associated at the inlet .
Good luck
